Deciphering the interaction mechanisms of Listeria monocytogenes and Salmonella enterica with the food matrix

• Applicants: Dr. Irene Esteban Cuesta; Dr. Irmak Sah, Ph.D.
• Subject Area: Veterinary Medical Science ; Microbial Ecology and Applied Microbiology
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 494875429

Salmonella enterica and Listeria monocytogenes are two of the most important foodborne pathogens worldwide. In 2019, salmonellosis was the second most commonly reported zoonosis, while listeriosis was one of the two most severe diseases with the highest case fatality. As infection mainly results from the consumption of contaminated food, in order to cause disease, both pathogens need to survive and, in many cases, grow in the food matrix. Therefore, understanding the molecular mechanisms behind their resilience towards the stress conditions in different food matrices is crucial, not only for developing effective methods to reduce pathogen fitness in various foods but also to assess food safety risks better. Many studies have investigated the stress response mechanisms of these pathogens, mostly using laboratory strains in laboratory media without the complexity of the food matrix. We aim to address this research gap by screening S. enterica and L. monocytogenes random mutants on relevant food matrices to analyze genome-wide fitness effects of individual genes and identify the metabolic pathways involved. Transposon (Tn) mutagenesis is a method to create random mutations in a genome, which can be used to define genes required for growth or survival in diverse conditions. Combining this method with next-generation sequencing, Transposon Insertion Sequencing (TIS), enables analysis of gene functions across the whole genome in a single experiment. Using classic Tn mutagenesis and two TIS methods, we will efficiently analyze the genomic basis of the interactions of these pathogens with related food matrices in a high throughput manner. We currently dispose of three TIS libraries on different S. enterica serotypes and a classical Tn mutagenesis library of L. monocytogenes. We will screen these libraries on the food matrix, generate hypotheses on specific molecular mechanisms, and confirm candidate genes to create a metabolic map for individual pathogen-matrix interactions. In addition, we aim to create a TIS library on L. monocytogenes for the first time and expand the S. enterica TIS libraries to two further serotypes, which would help understand differences between serovars and to refine and expand the metabolic map. The results of this study will elucidate the molecular mechanisms of survival of two important foodborne pathogens in the food matrix. and provide data for science-based preventive strategies. It will also be an investment into years of future research to address questions of survival within the food chain.

• DFG Programme: Research Grants